Process for construction of bridges, in particular motorway flyovers

ABSTRACT

For constructing a bridge having two successive piers and a continuous deck resting thereon and made of consecutive prefabricated segments, two deck portions or &#39;&#39;&#39;&#39;beams&#39;&#39;&#39;&#39; - each of which rests upon a provisional horizontal platform via vertical jacks, over the upper face of each of the two piers and out of contact with said face- are separately prepared, then assembled together by horizontally moving said two deck portions towards each other and fastening them together, the continuous deck thus formed being then lowered by means of the jacks until it rests on the two piers.

United States Patent Muller 1 1 May 13, R975 [541 PROCESS FOR CONSTRUCTION OF 3,571,835 3/1971 Buechler 14/1 Y 3.832.748 9/1974 Ogletree BRIDGES IN PARTICULAR MOTORWA 3,845,514 11/1974 Wagner 14/1 FLYOVERS Jean Muller, Suresnes, France Societe dEtudes de Genie Civil et de Techniques Industrielles, Paris France Filed: Sept. 20, 1974 Appl. No.: 507,798

Inventor:

Assignee:

Foreign Application Priority Data Sept. 24 1973 France 73.34133 References Cited UNITED STATES PATENTS Mladyenovitch 14/7 X OTHER PUBLICATIONS Civil Engineering; Vol. 11, No. 3; March 1941; Pgs.

Primary Examiner-Nile C. Byers. Jr. Attorney, Agenl, or F irm-Staas and Halsey [57] ABSTRACT For constructing a bridge having two successive piers and a continuous deck resting thereon and made of consecutive prefabricated segments. two deck portions or beams" each of which rests upon a provisional horizontal platform via vertical jacks, over the upper face of each of the two piers and out of contact with said faceare separately prepared. then assembled together by horizontally moving said two deck portions towards each other and fastening them together, the continuous deck thus formed being then lowered by means of the jacks until it rests on the two piers.

4 Claims 10 Drawing Figures PATENTED HAY I 3 i975 SHEET 30F 3 y 14 2 2 22 5/ 24 D 1 j t k l L r I Q Q Q 1 1 if: I, I L. 2/ 25 FIG: 9 W 50 a FIG: 10 d 5 4 6 PROCESS FOR CONSTRUCTION OF BRIDGES, IN PARTICULAR MOTORWAY FLYOVERS The present invention relates to the construction of bridges with at least two piers and a continuous deck resting on the said piers, the said deck comprising at least one central span between two successive piers and two lateral spans extending respectively on either side of the said central span.

It applies more particularly, although not exclusively, to the construction of short-span bridges with two piers intended for construction in large numbers, which is the case with flyovers which cross motorways, for example.

Aknown process for constructing the decks of such bridges comprises assembling and fastening by means of prestressing reinforcements a plurality of prefabricated elements or segments each having two opposed end faces, each segment being applied with one of its end faces against the adjacent end face of the immediately adjacent segment.

In this respect, it is particularly advantageous for each end face ofa segment to be an exact reverse of the end face of the adjacent segment against which it is applied. The segments can then be assembled in accordance with the conjugate joints technique, without interposition of any cast or caulked mortar joint, or only using a very thin joint formed, for example, of a quick-setting polymerizable resin adhesive, which permits a considerable saving of time. Such segments made of concrete or similar material can be obtained, in known manner, by moulding the said segments against each other at the pre-fabrication stage, the end face of one finished segment acting as a mould for the next segment to be prefabricated.

In the above-mentioned known process, a deck portion or beam resting on a pier is formed in accordance with the cantilever method by successively placing segments symmetrically in position on either side of the said pier. When two symmetrical segments have been placed in position, they are finally fastened to the portion of the beam already formed by the use of one or more prestressing reinforcements which pass through the said beam portion and are anchored at their two ends in the two segments in question. This process is repeated each time a pair of segments is placed in position.

It results from the above that, when the deck is finished, the prestressing structure associated with it will have been essentially determined by the method of construction selected for the beam. Therefore it will not have the optimum characteristics which would have been adopted if the intermediate deck construction phases could have been disregarded. In particular this structure will comprise a much larger number of reinforcements and anchorages than would have been sufficient simply to ensure the strength of the deck in use and which has been imposed by the need to ensure the strength of the beam at all the intermediate stages of its construction. Moreover, the pattern of these reinforcements will not be the one which would have enabled optimum stress distribution to be obtained along the finished deck in use. In fact this pattern must take into account the fact that during the intermediate phases of construction of the beam, the portion of the beam adjacent to the pier is very subject to the action of the inherent weight of the two arms of the beam,

while the two ends of the beam (and in particular the one which in the finished construction will form the crown of the central span of the deck) are only under a very low load.

A further disadvantage of the above-mentioned known process resides in the impossibility of applying the conjugate joints technique mentioned above to the assembly of the two beams in the crown zone of the central span of the deck. Thereis therefore occasion in this zone to place in position a conventional keying joint of cast or caulked mortar, which entails a not negligeable time loss, especially in the case of constructions such as motorway flyovers which are to be mass produced.

The present invention is intended to at least mainly eliminate the disadvantages mentioned. It is more particularly intended to ensure the stability and strength of the deck during all the intermediate phases of its construction, while permitting optimisation of the prestressing structure associated with the said deck. It is also intended to permit application of the conjugate joints technique in the crown zone of the central span of the said deck.

In accordance with the invention, the following procedure is adopted to construct the deck of a bridge with at least two piers and a continuous deck of the type mentioned in the preamble:

adjacent to each pier is erected a falsework having a I substantially horizontal upper platform on which are arranged substantially vertical main jacks having in their lower portions sliding or rolling organs enabling the said jacks to slide or roll on the said platform;

the segments of a deck portion which comprises a fraction of the central span and at least a fraction of the lateral span associated with the pier in question are then placed successively in position over each of the said platforms, bearing on the said platform by means of the said main jacks, and the said segments are joined together by means of temporary fastening organs, the deck portion thus formed which is supported by the said main jacks then extending over the upper face of the pier in question and without contact with the said face;

the main jacks supporting at least one of the two deck portions associated with two successive piers are then made to slide on their platform, so as to move together the said two deck portions until their mutually facing end faces come into contact with each other;

the segments of the assembly formed by the said deck.

portions are permanently fastened together by means of prestressing reinforcements distinct from the temporary fastening organs used previously, so as to form a continuous deck;

the said continuous deck is lowered by operating the said jacks until it rests on the piers of the bridge; and

the said temporary fastening organs are disassembled together with the falseworks equipped with their jacks.

Because, in the process in accordance with the invention, the final prestressing reinforcements are not used to ensure the strength of the deck during the intermediate phases of its construction, the number and the pattern of these reinforcements can be determined to satisfy the single condition that an optimum loading state from the point of view of stress distribution is obtained along the finished deck in use. Maximum economy of materials is thus obtained.

It will also be observed that the process in accordance with the invention for the first time enables the central span to be keyed by application of the conju gate joints technique and the conventional mortar joint to thus be eliminated. An appreciable amount of time 5 is saved due to this.

The following description with reference to the attached drawings given by way of a non-limiting example will lead to a good understanding of how the invention may be put into effect.

FIGS. 1 to 7 are diagrammatic elevations illustrating the successive phases in the construction of a bridge by the process in accordance with the invention.

FIG. 8 is an elevation to a larger scale of a falsework arranged adjacent to a pier and used for performing the said process.

FIG. 9 is a plan of the falsework shown in FIG. 8.

FIG. 10 is a diagrammatic side elevation showing an organ for temporary fastening of two segments.

Reference will firstly be made to FIG. 7 which shows the finished bridge.

In the example shown, this bridge is a bridge with two piers P and P, on which rests a continuous deck T comprising a central span between the two piers P and P and two lateral spans which extend respectively on either side of the said central span. In the example selected, this bridge acts as a flyover crossing the two carriageways of a motorway A. At its two ends, the deck T rests on abutments C and C arranged at the tops of two banks which border the motorway at this point.

The deck T is formed by assembly of a plurality of prefabricated elements or segments V V V v', v', v, made of concrete and joined by means of prestressing reinforcements such as cables I and 2. Each segment, such as V, (see FIG. I0) has two opposed end faces a and b and it is applied by one of its and faces a against the adjacent end face b of the immediately adjacent segment V The end face b of the segment V is an exact reverse of the end face a of the segment V so as to permit assembly of the said segments in accordance with the conjugate joints technique mentioned above.

Reference will now be made to FIGS. 8 and 9 which show to a larger scale a falsework used for performing the construction process in accordance with the invention.

This falsework comprises two temporary supports B and B upon which rests a substantially horizontal upper platform D. In the example shown, the temporary support B is formed by a framework fixed temporarily but rigidly, for example by means of prestressing bars 3, to one of the two piers of the. bridge, for example the pier P, supposed already constructed. The temporary support B comprises an auxiliary pier resting on the ground adjacent to the said pier. The platform D is formed of an assembly of two cross-pieces parallel to the longitudinal axis of the deck.

On this platform D are arranged two groups of substantially vertical jacks, advantageously of the hydrau lic type, namely a group of four main jacks Ill, I2, l3, l4 and a group of four auxiliary jacks 211, 22, 23, 24. As a concrete example we shall specify here, supposing that the weight of each segment is between 18 and 25 t, that the main jacks are each 100 t jacks while the auxiliary jacks are each 25 tjacks.

Each main jack Ill (12, 13, I4) is carried by a base Ilia (12a, 113a, 114a) which rests on the platform D by means of a sliding organ or runner trad (1211a, 13ml, I I

ll tlaa) made of a material witha low coefficient of friction such as polytetrafluorethylenei In this positionthe platform D is itself provided with a slide-track G with a low coefficient of friction. It isnaturally self-evident that the above-mentioned sliding organs could be replaced, where necessary, by rolling organs such as ball 7 bearing systems. The mainjacks 1t, 12, 13, 14 can thus slide or roll on the platform Dparallel to the longitudinal axis of the deck indicated by the arrow F.

The auxiliary jacks 21, 22,23, 24 rest on the platform g D without interposition of sliding or rolling organs. In i the example shown, the jacks 21 and 23 are carried by g a common base 30, while the jacks 22 and 24'- are carried by a similar base 31. The auxiliary jacks are ar-* ranged between the main jacks and they are separated from each other longitudinally of the deck by a smaller distance (211-23) than that (Ill-I3) between the said main jacks.

The successive phases in the construction ofthe bridge by the process in accordance with the invention will now be described with reference to FIGS. 1 to 7.

FIG. 11 shows a first phase of the process, during,

which, after erection adjacentto a pier P ofa falsework I3,-B -D (similar to that described with reference to 7 FIGS. 7 and 8) equipped with its two groups of jacks 11,12, 13, I4 and 2ll, 22, 23, 24, a first segment V adjacent to the said pier is firstly placed on all fourauxiliary jacks 211, 22, 23, 24.

The segment V which is the pier segment, is athen placed in position beside the segment V and these two ment V which is mounted beside it in cantilever, the

said segment V can be anchored temporarily to the 7 platform D, for example by means of prestressing rods (not shown). I

FIG. 2 shows a second phase of the process in accor 7 dance with which firstly a segment Vgsymmetrical with the segment V relative to the segment V isplaced in position and the segments V and V are joined by Y means of temporary fastening organs 41 similar to those,

described above. The assembly of the {three segments V,, V and V thus still rests on the four auxiliary jacks f 21, 22, 23, 24. The whole of the load is then transferred 1 7 onto the four main jacks Ill, 12, I3, 14 so as to free the four auxiliary jacks which play. no further part in. the subsequent operations.

A segment V is then placed in position in cantilever I next to segment V and the said segments V and V, are q joined by means of temporary fastening organs 4, simi-]' lar to those which have already been described.

FIG. 3 shows a third phase of the process in accordance with which the operation of positioningand temporarily fastening the segments V V V over the platform D are continued, still bearing on the said plat? form by means of the main jacks Iii, 112, 13,114 until a deck portion or beam has been assembled which comf prises a fraction (in practice, half) of the central span and at least a fraction of the latera l span associated with the pier P. j v e I g V It will be observed 4 and this remark is'es'sential that the main jacks 11, 1 2, 13, l4are so adjusted that the said deck portion or beam, which'rests on the said the pier P are repeated for the beam associated-with the pier P, as shown in FIG. 4. In this figure the segments are marked with the references V' V' V the falsework with the references B' B -D', the main jacks with the references lll2l3'l4' and the temporary fastening organs with the references 4'.

FIG. 4 shows a fourth phase of the process, in accordance with which the two deck portions or beams V,-V --V -V V and V' -V' V' -V V, carried respectively by the two falseworks B -B -D and B',B' D' are moved together by sliding or rolling their main support jacks 11-12-13-14 and/or l1l2- '1314 horizontally on their respective platforms D and D until the mutually facing end faces of these beams contact each other. All that is necessary to cause this horizontal displacement is to apply a modest horizontal force to at least one of the said beams, taking into account the presence of the sliding runners llaa, l2aa, and the sliding surfaces G. A system of traction bars or horizontal rams (not shown) can advantageously be employed for this purpose. This horizontal displacement may also result simply from the use of the prestressing reinforcements 1, described in the next phase of the operations.

FIG. 5 shows a fifth phase of the process in accordance with which the segments of the assembly formed by the two beams thus brought together to form a continuous deck are permanently fastened together. For this purpose prestressing reinforcements 1 such as cables are employed, distinct from the temporary fastening organs 4 or 4' described above and passing inside the material forming the segments. Part of the assembly of the said temporary fastening organs can then be disassembled, if required.

FIG. 6 shows a sixth phase of the process in accorthe deck are completed by addition of end segments such as V and V' designed to rest on the end abutments C and C. On the upper faces of the piers P and P is then placed an elastic, e.g. synthetic rubber, sheet designed to act as a pseudo articulation in the construction in use. All the main jacks ll, 12, l3, l4 and 11, 12', 13, 14 are then collapsed so that the whole continuous deck T formed as just described is lowered until it rests on the two piers P and P. All the temporary connecting organs 4 and 4' which have not already been taken down at the end of the fifth phase are then disassembled, together with the falseworks B,B -D and B' -B -D equipped with their jacks. All these accessories can thus be reused to construct the next bridge.

FIG. 7 shows the finished bridge. This figure shows other permanent prestressing reinforcements 2 passing through the end segments V and V,,.

It will be noted that in the continuous deck T thus formed, the permanent prestressing structure 1 has played no part in stabilizing and strengthening the two beams during assembly. It has therefore been possible to calculate it, as explained above, simply to ensure the strength of the deck in use, under the best conditions fior'ri the point of view of stress distribution.

Furthermore a considerable amount of time is saved, due'lon the one hand to the sinaller number of perma- :nent prestressing reinforcements which requires to be dance with which, if necessary, the two lateral spans of i used and on the other hand to, the elimination of the conventional keying joint of the central span.

The invention has been described, as a non-limiting example, in its application to the construction of a bridge with two piers and three spans, but it is selfevident that it is also applicable to the construction of bridges (or similar constructions such as elevated highways) with multiple spans resting on more than two piers.

It is self-evident that the embodiment described is only an example and that it would be possible to modify it, in particular by substitution of equivalent techniques, without thereby departing from the scope of the invention.

I claim: 1. In a process for construction of a bridge with at least two piers and a continuous deck resting on the said piers, the said deck comprising at least a central span between two successive piers and two lateral spans extending respectively on either side of the said central span, the said process in particular comprising, to construct the said deck, assembling and fastening by means of prestressing reinforcements a plurality of prefabricated segments each having two opposed end faces, each segment being applied with one of its end faces against the adjacent end face of the immediately adjacent segment, the improvement comprising the following successive steps:

adjacent to each pier is erected a falsework having a substantially horizontal upper platform on which are arranged substantially vertical main jacks provided in their lower portions with sliding or rolling organs enabling the said jacks to slide or roll on the said platform; the segments of a deck portion which comprises a fraction of the central span and at least a fraction of the lateral span associated with the pier in question are then placed successively in position over each of the said platforms, bearing on the said platform by means of the said main jacks, and the said segments are joined together by means of temporary fastening organs, the deck portion thus formed which is supported by the said main jacks then extending over the upper face of the pier in question and out of contact with the said face;

the main jacks supporting at least one of the two deck portions associated with two successive piers are then made to roll or slide on their platforms, so as to move the said two deck portions towards each other until their mutually facing end faces contact each other;

the segments of the assembly formed by the said deck portions are then permanently fastened together by means of prestressing reinforcements distinct from the temporary fastening organs used before,'so as to form a continuous deck;

the said continuous deck is lowered by operating the said main jacks until it rests on the piers of the bridge; and

8 each other longitudinallyof the deck by tance than that between the said main jacks; and wherein each of the deck portions is placed in position by firstly resting it on the said auxiliary jacks and then I I transferring the load onto the said main jacks.

4. Process in accordance with claim 1, wherein in each falsework the upper platform is made to rest on two temporary supports one of which comprises a frame fixed temporarily to a pier of the bridge and the, other an auxiliary pier resting on the ground adjacent to the said pier.

asmaller dis- 

1. In a process for construction of a bridge with at least two piers and a continuous deck resting on the said piers, the said deck comprising at least a central span between two successive piers and two lateral spans extending respectively on either side of the said central span, the said process in particular comprising, to construct the said deck, assembling and fastening by means of prestressing reinforcements a plurality of prefabricated segments each having two opposed end faces, each segment being applied with one of its end faces against the adjacent end face of the immediately adjacent segment, the improvement comprising the following successive steps: adjacent to each pier is erected a falsework having a substantially horizontal upper platform on which are arranged substantially vertical main jacks provided in their lower portions with sliding or rolling organs enabling the said jacks to slide or roll on the said platform; the segments of a deck portion which comprises a fraction of the central span and at least a fraction of the lateral span associated with the pier in question are then placed successively in position over each of the said platforms, bearing on the said platform by means of the said main jacks, and the said segments are joined together by means of temporary fastening organs, the deck portion thus formed - which is supported by the said main jacks - then extending over the upper face of the pier in question and out of contact with the said face; the main jacks supporting at least one of the two deck portions associated with two successive piers are then made to roll or slide on their platforms, so as to move the said two deck portions towards each other until their mutually facing end faces contact each other; the segments of the assembly formed by the said deck portions are then permanently fastened together by means of prestressing reinforcements distinct from the temporary fastening organs used before, so as to form a continuous deck; the said continuous deck is lowered by operating the said main jacks until it rests on the piers of the bridge; and the said temporary fastening organs and the said falseworks equipped with their jacks are disassembled.
 2. Process in accordance with claim 1, wherein the said temporary fastening is effected by means of temporary prestressinig reinforcements distinct from the prestressing reinforcements used for permanent fastening and passing outside the material forming the segments.
 3. Process in accordance with claim 1, wherein on each of the said platforms are also arranged, in addition to the main jacks, substantially vertical auxiliary jacks arranged between the main jacks and separated from each other longitudinally of the deck by a smaller distance than that between the said main jacks; and wherein each of the deck portions is placed in position by firstly resting it on the said auxiliary jacks and then transferring the load onto the said main jacks.
 4. Process in accordance with claim 1, wherein in each falsework the upper platform is made to rest on two temporary supports one of which comprises a frame fixed temporarily to a pier of the bridge and the other an auxiliary pier resting on the ground adjacent to the said pier. 